Its very easy to file your own UK trademark application online. Just remember to check that you are on the .gov.uk web page at all times. The UK intellectual property office have gone to a lot of trouble to make their system easy to use so its a waste to use a third party portal and add to your costs. The main problem is deciding how to draft your specification of goods. First you have to decide what goods you want to protect the brand for. This is usually what you make and sell. Its what your clients or customers pay for. If you provide a service, it can be more challenging. Having decided on that you next need to work out what class or classes cover what you do. Everything has to be somewhere and there is an international classication of 45 classes into which all commercial activity has to fit. They call it the Nice Classification. You can imagine the excitement of those international conferences where officials from trade mark registries around the world discuss where knitted tea cosies should be (21) and whether silver spoons are in the same class as steel ones (yes 8 unless they are for serving 21).
One of the best tools to help you, if you have not already decided it might be wise to consult an expert, is called TMClass – a free gift from the excess profits made by the European Union Intellectual Property Office. They have a tool to help you verify your chosen list but do remember we use ; between items.